Concept Notes
1. Kirchhoff’s Current Law (KCL)
- Statement:
At any junction (node) in an electrical circuit, the sum of currents entering is equal to the sum of currents leaving. - Mathematically:
✔️ Based on conservation of charge.
Example:
At a node, currents are 
.
By KCL:
2. Kirchhoff’s Voltage Law (KVL)
- Statement:
In any closed loop of a circuit, the algebraic sum of all voltages is zero. - Mathematically:
✔️ Based on conservation of energy.
Sign convention:
- Voltage rise → positive
- Voltage drop → negative
Example:
A loop with 
:
3. General Applications
- KCL → used in nodal analysis.
- KVL → used in mesh analysis.
- Both laws are fundamental to circuit theory.
⚙️ Formulas
KCL:
KVL:
Ohm’s Law (for solving circuits):
Power relation:
🧮 Solved Example
Q: In a circuit loop:
- Battery =
- Resistors =
in series - Find current.
Solution:
Total resistance = 
By KVL:
🔟 10 MCQs
Q1. KCL is based on:
a) Conservation of energy
b) Conservation of charge
c) Conservation of power
d) Ohm’s law
Q2. KVL is based on:
a) Conservation of energy
b) Conservation of charge
c) Conservation of momentum
d) None
Q3. The algebraic sum of currents at a node is:
a) Always zero
b) Always positive
c) Always negative
d) Cannot be determined
Q4. In a loop with 
battery and two resistors 
in series, current is:
a) 
b) 
c) 
d) 
Q5. If 
and 
, then 
= ?
a) 3A
b) 5A
c) 7A
d) 10A
Q6. In KVL, sum of all voltages in a closed loop is:
a) Zero
b) One
c) Infinity
d) Cannot say
Q7. Which analysis is based on KCL?
a) Mesh
b) Nodal
c) Thevenin
d) Norton
Q8. Which analysis is based on KVL?
a) Nodal
b) Mesh
c) Superposition
d) Maximum Power Transfer
Q9. If current entering node = 
and currents leaving are 
, then 
a) 0.5A
b) 1A
c) 2A
d) 3A
Q10. A loop has resistors 
in series with 
battery. Find current.
a) 1A
b) 2A
c) 3A
d) 4A
✅ Answer Key
| Q No | Answer |
|---|---|
| Q1 | b |
| Q2 | a |
| Q3 | a |
| Q4 | b |
| Q5 | c |
| Q6 | a |
| Q7 | b |
| Q8 | b |
| Q9 | b |
| Q10 | b |
🧠 Explanations
- Q1: KCL depends on charge conservation.
- Q2: KVL depends on energy conservation.
- Q3: Net current at node = 0.
- Q4:
(Correct ans = 3A, correction made ✅). - Q5:
. - Q6: Always zero.
- Q7: Nodal → KCL.
- Q8: Mesh → KVL.
- Q9:
. - Q10:
.
🎯 Motivation
KVL and KCL are pillars of circuit theory.
- Almost every ECET problem in Networks, AC/DC circuits, Theorems is solved with these two rules.
- Strong grip → quick solving → more time saved for tough questions.
👉 Always write KCL/KVL equations step by step → you will never lose marks.
📲 CTA
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